For modern motor vehicles, improved environmental compatibility is also increasingly required on the part of the legislator. Thus, for example, it is common practice to replace the previously prevailing leaded solder connections in electronics assemblies by a joining technology without using lead. When constructing electronics assemblies that are used in motor vehicles in various ways in the form of controllers, sensors, navigation systems, entertainment systems or the like, individual components are arranged on circuit boards and are contacted w solder connections.
As is known from the prior art, the use of lead-free soldering materials facilitates the formation of filamentary tin crystals which are also called tin whiskers in English-speaking areas. Filamentary tin crystals preferably grow on galvanically deposited layers and can reach a length of several millimeters which, in compactly arranged components, can cause short circuits between adjacent soldering surfaces and as a result, in the worst case, entire assemblies can fail or only work faultily. In addition to the resulting maintenance costs, this also poses a safety risk since, for example, anti-lock braking systems, airbag systems or similar assemblies are safety-relevant components. Potential failure of assemblies caused by whiskers can either be prevented by avoiding the whisker formation during the tin deposition, or reduced.
From DE 19755185 A1, an aqueous, strongly acidic displacement bath is known for current-free deposition of tin on copper, which in a bath solution of dissolved substances contains tin in the form of a tin-II salt, thiourea or a derivate, 2-thiohydantoin, a fine-grain additive for tin, an emulsifier for the fine-grain additive, if it is insoluble in water, and a surfactant.
It is at least one object is to enable restoring the function of an electronics assembly in the event of a short circuit caused by a filamentary tin crystal, without having to replace the electronics assembly. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.